Climate and landscape change favouring early rice agriculture and appreciable human impact: Evidence from sediment delta C-13 in eastern China

Kuahuqiao site, famous for its early rice cultivation, is taken to be a typical case of how agriculture emerged in a littoral environment in the early Holocene. However, the lack of fire history and local climatic reconstruction has hindered the detailed picture of agricultural origins and development. Here we report new records of TOC, BC, delta(CTOC)-C-13, delta C-13(BC), and C/N, alongside published pollen and charcoal data. Our delta(CTOC)-C-13 and C/N confirm the previously-proposed formation of wetlands, which offered favorable landscapes for rice paddy agriculture, prior to the appearance of the Kuahuqiao culture. Based on BC, delta(CTOC)-C-13, and delta C-13(BC) records we suggest a hotter but drier climate that would have benefited rice agriculture by augmenting the distribution of wild rice and C-4 herbs. In addition, delta(CTOC)-C-13 shows a decreased C-3/C-4 ratio as a signal of human occupation with manipulation of forest for hunting-gathering or/and land clearance for agriculture. Combined delta C-13(BC) and BC records oppose the proposal of intense fire use in early agriculture and suggest that fire use was constrained to domestic purposes. Flood events which seem to have terminated the Kuahuqiao culture left impressions in T-OC, BC, delta(CTOC)-C-13, delta C-13(BC).